Coating removal method

ABSTRACT

A method of removing solid surface materials from a solid substrate which comprises applying to the surface materials, preferably as a mixture, water and a relatively volatile, heavier-than-water, water-immiscible solvent for the surface material, preferably in a volumetric ratio of about one part water per part solvent. Water forms an overlying layer above the solvent such that the solvent softens the surface material and there is little solvent loss by vaporization. Subsequently the surface material can be removed by conventional means from a foundation or solid substrate left fit for resurfacing. A preferred solvent is carbon tetrachloride.

United, States Patent Panther [54] COATING REMOVAL METHOD [72] Inventor:Eugene M. Fauber, Hammond, Ind.

[73] Assignee: Atlantic Richfield Company, New York,

[22] Filed: Mar. 30, 1970 [211 App]. No.: 23,978

[52] U.S. Cl... ..134/6, 94/22, 94/23,

134/38, l34/40,-134/42 [51 Int. Cl. ...B08b 3/08, B08b 3/10 [58] FieldolSearch ..134/6, 5, 38, 40,42;

-2l/60.5 R, 60.5 A; 94/22, 23

[56] References Cited UNlTED STATES PATENTS 1,074,747 10/1913 Rowe..2l/60.5R 1,913,647 6/1933 Vallee ....134/40 151 3,664,871 51 May 23,1972 2/1960 Kburg 134/40 X 12/1970 Lowell ..94/23 X 57 ABSTRACT A methodof removing solid surface materials from a solid substrate whichcomprises applying to the surface materials, preferably as a mixture,water and a relatively volatile, heavier-than-water, water-immisciblesolvent for the surface material, preferably in a volumetric ratio ofabout one part water per part solvent. Water fonns an overlying layerabove the solvent such that the solvent softens the surface material andthere is little solvent loss by vaporization. Subsequently the surfacematerial can be removed by conventional means from a foundation or solidsubstrate left fit for resurfacing. A preferred solvent is carbontetrachloride.

10 Claims, No Drawings COATING REMOVAL METHOD This invention relates toa method of removing solid surface materials from their foundations orsolid, supporting substrates.

Many solid substrates or supporting surfaces are coated with a materialthat subsequently needs to be removed from the substrate for replacementof the exposed surface coating, for example, road surfaces whichtypically contain natural or synthetic binders for holding togetherpaving aggregates. As examples, the binder may be a natural asphalticmaterial or a synthetic resinous solid. Commonly in making a roadsurface, hot binder material is mixed with mineral aggregate such ascrushed stone, gravel, etc. or sand or combinations thereof, and themixture is placed while in a heated condition onthe wearing surface of apavement or other solid, supporting road bed. The surface is then rolledsmooth and allowed to cool. Such paving compositions gradually hardenover a period of years due for example to losses of volatile materialsfrom and oxidation of the binder material. These losses cause the bindermaterial to become dry, brittle and unsatisfactory as a binder andresult in cracking, raveling and general deterioration of the pavementsurface so that it becomes unfit for further use. When pavement surfacesare in this condition, it is customary to either apply an additionalincrement of new road over the old road and tack the two together withliquid asphalt or road oil, or remove the unsatisfactory dry and brittleasphaltic surface material from its foundation. If the surface isremoved, it can be discarded and a fresh new surface relaid on thefoundation, or the torn-up material can be reduced in size by mechanicalgrinders or crushers and blended with for example a binder cutback oiland relaid as a new surface.

Currently, removal of deteriorated road surface materials of theforegoing described types is often effected by softening the material byheat and removing it from its foundations by, for example, mechanicalscraping. Such methods, however, are not wholly satisfactorv becausethey require special equipment not always possessed by road contractors.Also the expense of heating and the necessity of maintaining the surfacematerial heated until the time for removal by mechanical means istroublesome to accomplish and can give rise to costly and time-consumingreheating operations.

The method of the present invention provides for the efficient andrelatively inexpensive removal from the supporting substrate of theforegoing described surface materials. According to the procedure, waterand a relatively volatile solvent for the binder, which solvent iswater-immiscible and has a specific gravity greater than water, areplaced on the surface material to be removed. Preferably, the water andsolvent are combined and then placed on the surface, and such mixturecan be maintained under agitation until being placed on the surface inorder that the solvent and water remain mixed. in any event the mixturemust be unstable so that when placed on the surface material the solventcontacts the binder and the water forms a layer over the solvent whichreduces solvent loss through volatilization that would otherwise occurunder the ambient conditions of temperature and pressure normally usedin the removal operation. The solvent and water can also be applied tothe surface sequentially in either order, but the use of thesolvent-water mixture is preferred. In any event, the solvent contactsand softens the binder and the overlying water layer serves to holdsolvent losses and costs to a minimum. After the binder is softened thesurface material can be mechanically removed as by cutting, scraping orcombinations of such treatments, and it has been found that themechanical removal operations are significantly enhanced by the use ofthe pre-softening procedure. After the removal, the substrate is readyto be re-surfaced. The method of the present invention is thus simple,effective and economical and the water and the heavier-than-watersolvent can be applied to the surface by means of conventional equipmentused for distributing asphalt cements, cutbacks andemulsions. Mostpaving contractors possess such equipment and the adoption of the methodof this invention will require the purchase of little, if any,additional equipment.

The heavier-than-water, normally liquid solvent for the binder materialcan be a lower alkyl polychloride such as methylene chloride,chloroform, etc., but preferably is carbon tetrachloride and thespecific gravity of the solvent is usually at least about 1.2,preferably at least about 1.4. The solvent is significantly morevolatile than water and usually has a boiling point at atmosphericpressure of below about F., often below about 80F. The amount of solventemployed is sufficient to give the desired softening of the binder inthe area of the surface treated, while the amount of water used isadequate to provide an essentially continuous layer over the solvent onthe surface being treated. The volumetric ratio of the water to solvent,whether applied to the surface separately or as a mixture is often about0.1 to 10 parts water per part solvent. Often the ratio is about 0.2 to5 parts water per part solvent, preferably about 0.5 to 2 parts waterper part solvent. Conveniently the mixture is applied to the surface inan amount of about 0.1 to 5 gallons, preferably about 0.5 to 2 gallons,per square yard of distribution area. Both the volumetric ratio and therate of application of the mixture can vary depending on each other andon such factors as the area and type of material to be removed. Thedepth and amount of material to be softened for removal can becontrolled by the volumetric ratio of the mixture, the rate ofapplication and soaking time prior to removal. As noted above, removalcan be by mechanical scraping and any underlying material softened butnot desired to be removed can be restored to its original condition byallowing time for the solvent that has contacted the material toevaporate.

The surface materials which can be removed by the method of thisinvention are solids at ambient conditions and are for the most partsoluble in the solvent employed. Asphalts used in surface materials forexample as binders in paving compositions, are usually recovered asresidua or as bottoms from the distillation of crude mineral oils. Theseasphalts often have a gram, 5 second penetration value at 77F. (ASTM D5)below about 300 and are usually applied as hot mix binders for mineralaggregates. Asphalts with these characteristics are often called asphaltcements. Their penetration values can be as low as about 40 andpreferably up to about 200. The asphalts which can be removed accordingto the process of this invention are preferably at least about 99 weightpercent soluble in carbon tetrachloride at ambient conditions.

Among the asphalt-like surface materials which can be removed accordingto the method of this invention, i.e., those having characteristics suchas solubility in the solvent, e.g. carbon tetrachloride, and penetrationand softening point values comparable to the previously mentionedasphalts, are for example, thermoplastic, petroleum-derived hydrocarbonresins, produced for example by polymerization of an unsaturatedpetroleum fraction in a relatively viscous plasticizing oil such as anaromatic or naphthenic lubricating oil or a mixture thereof. Suchmaterials are described in U.S. Pat. No. 3,297,625, herein incorporatedby reference. Other materials such as natural and synthetic rubbers canbe added as desired to improve the properties of the surface coating.Asphalt-like binders can be prepared from a wide range of quantities ofsuch ingredients. For example, the binders can comprise say from about 1to 10, preferably about 1 to 6, parts by weight of a hydrocarbon rubbersuch as a styrene-butadiene rubber; from about 30 to 60 parts,preferably about 35 to 45 parts, by weight of a substantiallv completelypolymerized, thermoplastic petroleum-derived hydrocarbon resin having asoftening point (R&B) of about 220 to 300F., preferably about 220 to260F., a mixed aniline point of about 20 to 60C., preferably about 30 to40C., an iodine number of from about 70 to 160, an acid number up toabout 4 and a molecular weight of about 600 to 1500 as determined bycryoscopic means; and from about 35 to 60 parts by weight of mineral oilof lubricating viscosity. A suitable mineral oil has about 8 to 10 partsby weight of a relatively viscous aromatic oil perpart of naphthenicoil.

The following example serves to illustrate a specific use of the methodof this invention.

The surface to which the solvent-water mixture was to be applied was apaving mix containing three-eighths inch top size, densely gradedaggregate and 6.0-6.5 weight percent of an almost colorless syntheticpetroleum-derived hydrocarbon resin of the type described above andquite similar to asphalt and soluble in carbon tetrachloride to theextent of at least 99.0 percent. The pavement surface was inches to 1inch thick, very badly cracked and broken up and had been placed over anasphalt binder course. The surface had to be removed before resurfacingcould be effected.

A distributor normally used for distributing asphalt cements, cutbacks,or emulsions was filled with an approximate l to l volumetric mixture ofwater and carbon tetrachloride. The distributor was equipped withconventional mixing equipment which was used during the distributionperiod. The mixture was applied at a rate of 0.75 gallons per squareyard of surface with each distribution pass feet wide. Forty-fiveminutes elapsed before scraping began with a scraper conventionally usedfor grading stone roads. Scraping to a depth of three-fourths inchproceeded at the same rate in feet/sec. as the distributor had traveled.Removal of the surface was satisfactorily and easily accomplishedleaving a new surface acceptable for resurfacing. Some softening of thisnew surface (the asphalt binder course below the surface course)occurred, but in one hour after scraping, the carbon tetrachloride hadevaporated thereby restoring the new surface to its original condition.Similar results can be obtained when removing a paving as described inthe foregoing example, except that a paving grade petroleum asphalt issub stituted for the hydrocarbon resin binder.

Iclaim: l. A method of removing surface materials from a solid,

supporting substrate, said surface material containing a binder solublein a normally liquid solvent having a boiling point below F. atatmospheric pressure, which comprises contacting said surface with anormally liquid, water-immiscible solvent having a boiling point below90F. at atmospheric pressure and a specific gravity greater than that ofwater, said solvent in contact with said surface being in an amountsufficient to soften said binder and overlain by water, holding thesolvent and water on the surface to allow the solvent to soften thebinder, and mechanically removing the surface material from saidsubstrate.

2. The method of claim 1 wherein the solvent is a lower alkylpolychloride.

3. The method of claim 1 wherein the water and solvent are applied tothe surface as a mixture.

4. The method of claim 3 wherein the mixture has about 0.5 to 2 parts ofwater per part of solvent.

5. The method of claim 4 wherein the solvent is a lower alkylpolychloride.

6. The method of claim 5 wherein the solvent is carbon tetrachloride.

7. The method of claim 3 wherein the surface material is a road surfacecomprised of aggregate and a binder selected from the group consistingof asphalt and normally solid, petroleum hydrocarbon resins.

8. The method of claim 7 wherein the solvent is a lower alkylpolychloride.

9. The method of claim 8 wherein the solvent is carbon tetrachloride.

10. The method of claim 9 wherein the mixture has about 0.5 to 2 partsof water per part of a solvent.

2. The method of claim 1 wherein the solvent is a lower alkylpolychloride.
 3. The method of claim 1 wherein the water and solvent areapplied to the surface as a mixture.
 4. The method of claim 3 whereinthe mixture has about 0.5 to 2 parts of water per part of solvent. 5.The method of claim 4 wherein the solvent is a lower alkyl polychloride.6. The method of claim 5 wherein the solvent is carbon tetrachloride. 7.The method of claim 3 wherein the surface material is a road surfacecomprised of aggregate and a binder selected from the group consistingof asphalt and normally solid, petroleum hydrocarbon resins.
 8. Themethod of claim 7 wherein the solvent is a lower alkyl polychloride. 9.The method of claim 8 wherein the solvent is carbon tetrachloride. 10.The method of claim 9 wherein the mixture has about 0.5 to 2 parts ofwater per part of a solvent.